Optical circuits provide many advantages over traditional electrical circuits. They are much faster and potentially much smaller than Controlled Collapse Chip Connector (C4) and Multi-Chip Module (MCM) packages. Optical circuits may also be used in conjunction with electronic MCMs.
Optical circuits typically use laser light transmitted by optical fiber. For example, many optical circuits use edge-emitting lasers (EELs) aligned with optical fiber lying in horizontal grooves on a substrate. This configuration of lasers and optical fiber requires significant area on an optical circuit substrate.
Optical fiber is typically composed of an outer layer and an inner core. The outer layer generally has a slightly lower refraction angle (index of refraction) than the inner core. The different refraction angle keeps light traveling in the centrally-aligned core. An end of each optical fiber is typically aligned on the substrate with an EEL. The other end of the optical fiber may be aligned with a photodetector. Typically, in manufacturing these optical circuits, optical fiber and EELs have to be aligned manually. This may take 30 to 40 minutes per alignment according to current techniques.
While EELs are capable of emitting many wavelengths of light and capable of emitting wavelengths in single and multi modes, they are difficult to manufacture and have high power requirements. Vertical Cavity Surface Emitting Lasers (VCSELs) are much easier to manufacture and have lower power requirements. While some VCSELs may only be able to emit a limited number of wavelengths in multimode emissions, they may be used to direct laser light signals in a vertical direction (i.e., orthogonal to the substrate).
Conventional products are difficult to align with a VCSEL and guide light vertically through one or more substrates with minimal dispersion losses.